Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$177.85	4.204%	$185.3268	$185.33	$185.35	$185.30
Purchase #2	$85.63	4.182%	$89.211	$89.21	$89.20	$89.20
Purchase #3	$69.46	13.442%	$78.7968	$78.80	$78.80	$78.80
Purchase #4	$229.27	6.771%	$244.7939	$244.79	$244.80	$244.80
Purchase #5	$119.72	9.152%	$130.6768	$130.68	$130.70	$130.70
Purchase #6	$51.77	8.603%	$56.2238	$56.22	$56.20	$56.20
Purchase #7	$174.51	9.399%	$190.9122	$190.91	$190.90	$190.90
7 purchase totals =	$908.21		$975.9413	$975.94	$975.95	$975.90